Interpretive Summary: Farmers, agricultural nutrient management planners, and regulatory agencies need to know the nutrient supply characteristics of livestock manures. We sampled a new source of dairy manure from barns with compost bedded packs and measured manure density, nutrient content, and nitrogen availability. We found that these manure packs have similar density, which means that farmers can easily estimate how much manure there is to apply to their fields. Furthermore, we developed sampling procedures so farmers can determine nutrient content before the manure must be applied. This is not usually possible with other manures. We produced the first estimates of nitrogen availability from this manure and found that they were quite variable. Some of the farms had manure that temporarily tied up nitrogen, a situation that might reduce crop yield. Guidelines for typical solid dairy manure did a poor job estimating nitrogen availability from this new manure, making it clear that new guidelines need to be developed for this new type of manure.

Technical Abstract:
Compost-bedded-pack (CBP) dairy barns are relatively new, but CBP manure has not been characterized in detail and there are no published data on its N supply. We measured physical characteristics, nutrient concentration, N mineralization, and N supply to corn (Zea mays L.) of CBP manure from eight Minnesota farms. Concentrations of N, P, and K were generally higher than in typical solid dairy manure and were highly variable within and among barns. Average bulk density of CBP manure was 58.2 lb/cu ft. All CBP manures released a net addition of nitrate to soil during a 4-month-long incubation, but the four with highest C:N ratios (19 to 21) immobilized N for 30 to 60 days. In-field fertilizer N equivalents to corn ranged from 1.4 to 12.1 lb N/ton for quickly incorporated CBP manure but only -0.3 to 5.3 lb N/ton for fall-applied manure that was not incorporated until spring. Guidelines for solid dairy manure were not reliable for predicting N availability from CBP manure. Until validated prediction equations are available, we recommend that farmers apply moderate rates of CBP manure, incorporate immediately to improve net N supply, apply a basal rate of fertilizer N near planting time, and be prepared to sidedress additional fertilizer N based on recommended soil or plant analysis for their region.